Sen. Ben Nelson (D-Neb.), the last Democratic holdout on health care, excused himself for a tense phone call with a Nebraska anti-abortion activist. But what was supposed to be a short break in the negotiations Friday night turned into a 90-minute nail-biter.

With less than 12 hours until Majority Leader Harry Reid needed to introduce the revised bill, the chief domestic policy priority of the White House and Congress was still wobbling on the brink of collapse.

Sen. Chuck Schumer (D-N.Y.) milled around Reid’s office, popping Christmas cookies and fudge. Reid slumped in his chair. Two top administration aides raced back to the White House screening room to catch part of the Montana-Villanova football game, but had returned to the Capitol, where they were now waiting with a pair of nervous Democratic leaders.

Soon enough, Nelson walked through the doors.

“We can live with this,” he announced to the group.

And with that, Reid secured the 60th vote for the most sweeping social legislation in decades, all but assuring passage in the Senate this week.

It came at a high cost, and exposed the enduring truth of the Senate, where one senator can hold up legislation and bargain his way to “yes.”

Nelson certainly availed himself of the privilege.

His objections already had helped kill the government-run insurance option in the bill. He won an agreement that the federal government will forever pick up Nebraska’s share of a proposed Medicaid expansion, a deal worth about $100 million in the first decade, according to a Senate aide. He carved Nebraska’s non-profit insurers out of a proposed industry tax.

And he built new restrictions on federal financing of abortions into the bill, infuriating groups on both sides of the emotional issue and almost certainly touching off a withering fight over the limits when House and Senate Democrats hash out a final compromise.

Already, a leading abortion opponent in the House, Rep. Bart Stupak (D-Mich.), is saying he doesn’t think the language Nelson won in the Senate bill goes far enough. The co-chairs of the House abortion-rights caucus, Democratic Reps. Diana DeGette (Colo.) and Louise M. Slaughter (N.Y.), left open the possibility of opposing Nelson's change as well, saying they believe it might be unconstituional — all signs of how abortion might still emerge as an obstacle to a final deal on reforming the U.S. health system.

Nelson – like Sen. Mary Landrieu (D-La.), who picked up a $300 million Medicaid fix to ease her into supporting the bill last month– made no excuses Saturday for what Republicans blasted as a sweetheart deal.

“I always put Nebraska first,” he told POLITICO in an interview after his announcement. “But I looked at this through the standpoint of Nebraskans and the country.”

Asked how much he got, Nelson said, "Most. Enough. I didn't get exactly every penny I was after."

"There is a difference between holding out for something and holding up," he added. "I was holding out for something to make it better."

But some Republicans suggested that Nelson held out on abortion to advance the deal for his home state on Medicaid. "You gotta compliment Ben Nelson for playing, 'The Price is Right.' He negotiated a Medicaid agreement for Nebraska that puts the federal government on the hook forever," said Sen. Richard Burr (R-N.C.)

Nelson started with a list of must-have changes that he provided to Schumer.

Nelson said some were specific to Nebraska, like the Medicaid fix. Others, he said, would benefit people across the country, like an inflation adjustment to the $2,500 cap on tax-exempt contributions to Flexible Savings Accounts.

Nelson and Reid quietly opened their negotiations Wednesday night. At times on Thursday, Schumer was calling Nelson every 15 minutes, as part of what the Nebraskan called pre-negotiations. By nightfall, with progress being made, Reid asked Nelson to join a round of intensive talks Friday morning at 9:30.

Unlike during the talks in the House, where White House Chief of Staff Rahm Emanuel took the lead, the administration would be represented by two Senate veterans with deep ties to Nelson’s part of the country. Senior adviser Pete Rouse once worked for former Senate Majority Leader Tom Daschle (D-S.D.), and deputy chief of staff Jim Messina remains close to his former boss, Sen. Max Baucus (D-Mont.) Nelson had personal relationships with both of them.

Schumer also had developed a bond with Nelson in recent years. The senator from Brooklyn traveled to Nebraska last month to hunt with Nelson. It was the first time Schumer shot a gun, and he bagged three pheasants.

“We hunt together,” Nelson said, visibly delighted by the irony. “We may be an odd couple in a lot of respects but we share some of the same qualities in trying to solve things.”

By around noon Friday, Reid and Nelson came to agreement in four areas: the Medicaid carve out for Nebraska, the exemption for Nebraska non-profit insurers, an exemption for Medicare supplemental insurance providers, and indexing the Flexible Savings Accounts.

After a break for lunch, Reid turned to abortion.

Nelson and Chief of Staff Tim Becker, who had flown in from Nebraska, set up shop in one room of Reid’s suite. Sen. Barbara Boxer (D-Calif.) and her aides settled into another wing with Sen. Patty Murray (D-Wash.), the two senators there to represent Democrats who favor abortion rights.

The opposing senators never spoke with each other or sat at the same table. They negotiated through Reid and Schumer.

Through the afternoon and early evening, they appeared deadlocked. Both sides, in consultation with advocacy groups, rejected various offers.

They couldn’t get beyond differences between the so-called Stupak amendment in the House bill, which would require women who receive federal subsidies for insurance to seek out a separate abortion rider, and a proposal by Sen. Bob Casey (D-Pa.) requiring policyholders to opt-out of abortion coverage.

“I don’t know if we can do this,” Nelson said he told Reid at one point. “I’m running out of ideas.”

As he spent the day munching on almonds, peanuts and potato chips, Nelson said he eventually had what he described as a breakthrough. He turned over a piece of paper, and drew a line down the center.

“Why don’t we have two policies?” Nelson asked. “One with and one without.”

Nelson proposed that every state insurance exchange offer at least one plan that does not cover abortion, and policyholders could choose a plan with or without abortion coverage, unless states choose to ban it. Also, people who receive federal subsidies would need to write two separate checks as a way to ensure that none of the federal dollars went toward the abortion premium.

Nelson asked for a break. He left Reid’s office and called Julie Schmit-Albin, executive director of Nebraska Right to Life.

He spent 40 minutes walking her through the proposal, but didn't convince her. In fact, she was beside herself. Nebraska Right to Life endorsed Nelson in 2006, and rallied around him as he emerged as the lone Senate Democrat prepared to filibuster unless the bill included Stupak-style language.

Nelson described the compromise to Schmit-Albin as “Stupak-plus,” since it also includes tax credits to encourage adoption and benefits to help unwed mothers cope with their pregnancy. She didn’t buy it.

“If this is so good for pro-life, why would Sen. Boxer and Sen. Schumer agree to this?” Schmit-Albin said she asked Nelson. “I am personally devastated.”

It was a glimpse of the fury that groups on both sides of the abortion battle would soon unleash. But by that point, Nelson appeared to have his mind made up.

Back in Reid's office, however, Schumer thought they had lost him.

"We had been working on this so long," Schumer said in an interview Saturday. "I had been talking to Ben 10 or 12 times a day, and of course the week before we had the meetings of the Group of 10. Nine months, all of this work, all these compromises, down the drain, for one thing -- that would just be awful."

With snow beginning to fall, Nelson returned to Reid's office, and accepted the deal. They shook hands – and hugged, first with Reid, then Schumer. Boxer and Murray signed off on it, too.

Minutes later, President Barack Obama was on the line from Air Force One, flying from Copenhagen to Washington. With his signature issue rescued, the president wanted to offer his congratulations.